Traditionally , planets been put into one of two categories : bouldered or gas giant . However , research worker from the Harvard - Smithsonian Center for Astrophysics ( CfA ) have now announced the discovery of a third eccentric of planet : a flatulency dwarf . The research was describe inNatureand was stage today at the224th Meeting of the American Astronomical Association .
While our solar system is home to small rocky planets and vast gas monster , there are other types of planets elsewhere . Using data from NASA ’s Kepler mission , the researchers have discovered that small gas satellite are actually quite common around other lead . A planet ’s category is determined by the composition of the host star .
" We were particularly interested in examine the planetary authorities smaller than four times the sizing of Earth , because it includes three - one-fourth of the planets found by Kepler . That ’s where you ’ll find rough worlds , which are the only kind that we would consider potentially habitable , " lead author Lars A. Buchhave state in apress release .
Exoplanets are much too distant to detect the ignitor they contemplate , as they get wash out out by the glare of their host superstar . or else , Kepler is able-bodied to identify exoplanets and their size by how much light the planet block out when it transits the sensation . research worker use the planet ’s orbital radius and the mass of the virtuoso todetermine the major planet ’s mass . When pile and size have been determined , astronomers can calculate the density , which provides information about the composition of the planet .
This method acting is n’t without its faults , as dimmer and smaller planets closer to the sizing of Earth are considerably harder to reckon the mass . Buchhave ’s team circumvented this obstruction by measuring the metallic element content ( metallicity ) of the boniface star . As the planet were formed from the same material , the content of the principal is likely to match the content encounter in the planet .
After analyze 600 exoplanets around 400 wiz , they witness that there were clear divide lines regarding size of it and composition . Planets more than 3.9 times the size of it of Earth were most likely petrol giants , and anything smaller than 1.7 times the size of it of Earth was likely rocky . The group in the middle represents the gas dwarf , which have rocky gist that can collect gasolene , organise atmospheres thick with atomic number 1 and helium .
Distance from the wiz plays a role in how large the rocky core can develop before developing the blockheaded air , with planets more distant to the Sunday growing quite large before becoming a gas dwarf . This shows that there is no upper limit to the sizing of rocky planet .
to boot , the squad also find that small , rocky planets have metallicities standardised to our Sun , while system with more gaseous state giant star have about 50 % more metal than our Lord’s Day .
" It seems that there is a ' sweet smirch ' of metallicity to get Earth - sizing planet , and it ’s about the same as the Sun . That makes sense because at lower metallicities you have few of the building blocks for satellite , and at higher metallicities you tend to make flatulence giant or else , ” he added .
Of course , metallicity of a whizz is n’t the only gene that go into regularise which type of planets will be present in the system of rules ; there are many others to consider as well . to boot , as the data comes from Kepler that studies inner planets transiting the maven , it does not include data on some of the more distant exoplanets in the system , which may change the results . Future written report will utilize outer planets when more selective information is usable .
